/********************************************************************************
 * Copyright (C) 2019 TypeFox and others.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the Eclipse
 * Public License v. 2.0 are satisfied: GNU General Public License, version 2
 * with the GNU Classpath Exception which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 ********************************************************************************/
/*---------------------------------------------------------------------------------------------
*  Copyright (c) Microsoft Corporation. All rights reserved.
*  Licensed under the MIT License. See License.txt in the project root for license information.
*--------------------------------------------------------------------------------------------*/
// copied and modified from https://github.com/microsoft/vscode/blob/ba40bd16433d5a817bfae15f3b4350e18f144af4/src/vs/workbench/contrib/webview/browser/pre/service-worker.js
// @ts-check
const VERSION = 1;

const rootPath = self.location.pathname.replace(/\/service-worker.js$/, '');

/**
 * Root path for resources
 */
const resourceRoots = [rootPath + '/theia-resource', rootPath + '/vscode-resource'];

const resolveTimeout = 30000;

/**
 * @template T
 * @typedef {{
 *     resolve: (x: T) => void,
 *     promise: Promise<T>
 * }} RequestStoreEntry
 */

/**
 * @template T
 */
class RequestStore {
    constructor() {
        /** @type {Map<string, RequestStoreEntry<T>>} */
        this.map = new Map();
    }

	/**
	 * @param {string} webviewId
	 * @param {string} path
	 * @return {Promise<T> | undefined}
	 */
    get(webviewId, path) {
        const entry = this.map.get(this._key(webviewId, path));
        return entry && entry.promise;
    }

	/**
	 * @param {string} webviewId
	 * @param {string} path
	 * @returns {Promise<T>}
	 */
    create(webviewId, path) {
        const existing = this.get(webviewId, path);
        if (existing) {
            return existing;
        }
        let resolve;
        const promise = new Promise(r => resolve = r);
        const entry = { resolve, promise };
        const key = this._key(webviewId, path);
        this.map.set(key, entry);

        const dispose = () => {
            clearTimeout(timeout);
            const existingEntry = this.map.get(key);
            if (existingEntry === entry) {
                return this.map.delete(key);
            }
        };
        const timeout = setTimeout(dispose, resolveTimeout);
        return promise;
    }

	/**
	 * @param {string} webviewId
	 * @param {string} path
	 * @param {T} result
	 * @return {boolean}
	 */
    resolve(webviewId, path, result) {
        const entry = this.map.get(this._key(webviewId, path));
        if (!entry) {
            return false;
        }
        entry.resolve(result);
        return true;
    }

	/**
	 * @param {string} webviewId
	 * @param {string} path
	 * @return {string}
	 */
    _key(webviewId, path) {
        return `${webviewId}@@@${path}`;
    }
}

/**
 * Map of requested paths to responses.
 *
 * @type {RequestStore<{ body: any, mime: string } | undefined>}
 */
const resourceRequestStore = new RequestStore();

/**
 * Map of requested localhost origins to optional redirects.
 *
 * @type {RequestStore<string | undefined>}
 */
const localhostRequestStore = new RequestStore();

const notFound = () =>
    new Response('Not Found', { status: 404, });

self.addEventListener('message', async (event) => {
    switch (event.data.channel) {
        case 'version':
            {
                self.clients.get(event.source.id).then(client => {
                    if (client) {
                        client.postMessage({
                            channel: 'version',
                            version: VERSION
                        });
                    }
                });
                return;
            }
        case 'did-load-resource':
            {
                const webviewId = getWebviewIdForClient(event.source);
                const data = event.data.data;
                const response = data.status === 200
                    ? { body: data.data, mime: data.mime }
                    : undefined;

                if (!resourceRequestStore.resolve(webviewId, data.path, response)) {
                    console.error('Could not resolve unknown resource', data.path);
                }
                return;
            }

        case 'did-load-localhost':
            {
                const webviewId = getWebviewIdForClient(event.source);
                const data = event.data.data;
                if (!localhostRequestStore.resolve(webviewId, data.origin, data.location)) {
                    console.error('Could not resolve unknown localhost', data.origin);
                }
                return;
            }
    }

    console.error('Unknown message');
});

self.addEventListener('fetch', (event) => {
    const requestUrl = new URL(event.request.url);

    for (const resourceRoot of resourceRoots) {
        // See if it's a resource request
        if (requestUrl.origin === self.origin && requestUrl.pathname.startsWith(resourceRoot + '/')) {
            return event.respondWith(processResourceRequest(event, requestUrl, resourceRoot));
        }
    }

    // See if it's a localhost request
    if (requestUrl.origin !== self.origin && requestUrl.host.match(/^localhost:(\d+)$/)) {
        return event.respondWith(processLocalhostRequest(event, requestUrl));
    }
});

self.addEventListener('install', (event) => {
    event.waitUntil(self.skipWaiting()); // Activate worker immediately
});

self.addEventListener('activate', (event) => {
    event.waitUntil(self.clients.claim()); // Become available to all pages
});

async function processResourceRequest(event, requestUrl, resourceRoot) {
    const client = await self.clients.get(event.clientId);
    if (!client) {
        console.error('Could not find inner client for request');
        return notFound();
    }

    const webviewId = getWebviewIdForClient(client);
    const resourcePath = requestUrl.pathname.startsWith(resourceRoot + '/') ? requestUrl.pathname.slice(resourceRoot.length) : requestUrl.pathname;

    function resolveResourceEntry(entry) {
        if (!entry) {
            return notFound();
        }
        return new Response(entry.body, {
            status: 200,
            headers: { 'Content-Type': entry.mime }
        });
    }

    const parentClient = await getOuterIframeClient(webviewId);
    if (!parentClient) {
        console.error('Could not find parent client for request');
        return notFound();
    }

    // Check if we've already resolved this request
    const existing = resourceRequestStore.get(webviewId, resourcePath);
    if (existing) {
        return existing.then(resolveResourceEntry);
    }

    parentClient.postMessage({
        channel: 'load-resource',
        path: resourcePath
    });

    return resourceRequestStore.create(webviewId, resourcePath)
        .then(resolveResourceEntry);
}

/**
 * @param {*} event
 * @param {URL} requestUrl
 */
async function processLocalhostRequest(event, requestUrl) {
    const client = await self.clients.get(event.clientId);
    if (!client) {
        // This is expected when requesting resources on other localhost ports
        // that are not spawned by vs code
        return undefined;
    }
    const webviewId = getWebviewIdForClient(client);
    const origin = requestUrl.origin;

    const resolveRedirect = redirectOrigin => {
        if (!redirectOrigin) {
            return fetch(event.request);
        }
        const location = event.request.url.replace(new RegExp(`^${requestUrl.origin}(/|$)`), `${redirectOrigin}$1`);
        return new Response(null, {
            status: 302,
            headers: {
                Location: location
            }
        });
    };

    const parentClient = await getOuterIframeClient(webviewId);
    if (!parentClient) {
        console.error('Could not find parent client for request');
        return notFound();
    }

    // Check if we've already resolved this request
    const existing = localhostRequestStore.get(webviewId, origin);
    if (existing) {
        return existing.then(resolveRedirect);
    }

    parentClient.postMessage({
        channel: 'load-localhost',
        origin: origin
    });

    return localhostRequestStore.create(webviewId, origin)
        .then(resolveRedirect);
}

function getWebviewIdForClient(client) {
    const requesterClientUrl = new URL(client.url);
    return requesterClientUrl.search.match(/\bid=([a-z0-9-]+)/i)[1];
}

async function getOuterIframeClient(webviewId) {
    const allClients = await self.clients.matchAll({ includeUncontrolled: true });
    return allClients.find(client => {
        const clientUrl = new URL(client.url);
        return (clientUrl.pathname === `${rootPath}/` || clientUrl.pathname === `${rootPath}/index.html`) && clientUrl.search.match(new RegExp('\\bid=' + webviewId));
    });
}
